smtp1-fwd.ams.wordpress.com has no NS records.
NS records for this zone are defined at ams.wordpress.com.
NS records for this zone are defined at ams.wordpress.com.
Question and response
Question
dig smtp1-fwd.ams.wordpress.com. NS
Answer
The response has no answer records.
Authority
ams.wordpress.com. 300 SOA ns1.wordpress.com. hostmaster.wordpress.com. 2005071863 14400 7200 604800 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0